Modular dewar vessel for cryogenic use



April 6, 1965 M. D. ANDONIAN MODULAR DEWAR VESSEL FOR CRYOGENIC USEFiled April 9, 1963 INVENTOR. MARTIN D. ANDQNIAN fl/QQKM ATTOR NEYS FIGSUnited States Patent 3,176,473 MODULAR DEWAR VESSEL FOR CRYOGENIC USEMartin D. Andonian, Lexington, Mass. Andonian Associates, Inc., 26Thayer Road, Waltham, Mass.) Filed Apr. 9, 1963, Ser. No. 271,671

' 14 Claims. (Cl. 62-45) This invention concerns a vacuum-insulatedvessel for low temperature use. More particularly, it relates to amodular design for a vacuum-insulated multi-walled container for usewith cryogenic fluids such as liquid helium, hydrogen, nitrogen, etc.The modular design provides for ready disassembly of a double-Dewarcontainer for low cost manufacture, ease of repair or modification.

The advantages and utility to scientists of using liquefied gases suchas helium, etc., to study the behavior of various substances at very lowtemperatures have long been established. The most convenient method forachieving very low temperatures is to utilize the latent heat ofvaporization of materials having very low boiling points. Commercialavailablility of liquefied gases such as nitrogen, hydrogen, and heliumhas opened new avenues for scientific exploration.

As might be expected, the use of cryogenic liquids to achieve lowtemperatures has created new needs for apparatus to economically containthese fluids while providing access to the low temperature environmentassociated with them. Many designs for insulated vessels have appearedand are in current use. The majority of these designs are for specialpurpose applications, and have a common fault that once assembled, theyare extremely diflicult to disassemble for repair or modification.Certain special properties of liquid helium, specifically the propertyof essentially zero viscosity at temperatures below 2.l9 K., causenormal leak testing procedures to be inadequate. The thermal propertiesand high cost of liquid helium preclude testing prior to completeassembly. Thus, a leak occurring only when superfluid helium is presentcannot be detected, located, and

repaired without first assembling the vessel in its final form, and withprior constructions the disassembly for repair can require much time andexpense.

Moreover, the rapid rate of technological progress has resulted in veryrapid obsolescence of experimental equipment. The results of oneexperiment usually generate the need for other experiments requiringfacilities which may be diflerent from the original. Even a minordimensional change, for example, in the size of a sample, may renderuseless an expensive cryogenic facility. For example, a double-Dewararrangement used to house a sample for certain experiments may be whollyunsuitable for other samples or other experiments, although only slightdifferences in size or shape are involved. Substantial savings in timeand money could be achieved by modifying the vessel if it could bereadily disassembled and reassembled.

Accordingly, it is the primary objective of this invention to provide animproved double-Dewar vessel having a modular design which facilitatesmodification to accommodate a wide variety of low temperature operationsby means of interchangeable appendages and structures.

It is a further object of this invention to achieve this modular designwhile at the same time retaining thermal efficiency in the interest ofoperating economy.

It is a further object of this invention to provide a vessel of theabove type capable of economical fabrication and a high degree ofoperator safety. 7

Other objects will be in part obvious, and. in part pointed out indetail hereinafter.

This invention accordingly comprises the features of construction,combinations of elements and arrangement of parts which will beexemplified in the constructions the tubes 32 or the tube 16.

3,176,473 Patented Apr. 6, 1965 hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings, in which? a FIG. 1 is a crosssectional view showing details of construction of a cryogenic vessel,embodying the invention, comprising a modular Dewar body and a typicaltail section;

FIG. 2 is an exploded perspective View of the modular Dewar body of FIG.1, showing the manner in which it is readily disassembled andreassembled; and

FIG. 3 is an exploded perspective view of another tail section which maybe used with the Dewar body of FIGS. 1 and 2.

I For clarity, in the following discussion assume that the inner shellof the Dewar is filled with liquid helium and the thermal radiationshield is filled with liquid nitrogen, although this invention could beused with other cryogenic liquids.

With reference to the drawings, a Dewar vessel constructed in accordancewith the present invention is shown in FIG. 1. As illustrated therein,it comprises an inner helium chamber 1i bounded by an inner cylindricalhousing 12. The housing 12 is supported from a top plate 14 by means ofa thin-walled tube 16, which communicates with the exterior of thevessel for filling and, in some circumstances, insertion of elements tobe cooled.

Surrounding the housing 12 and separated from it by a vacuum insulationspace 18 is an annular nitrogen chamber 2%, bounded by a nitrogen shieldcomprising concentric'casings 22 and 24 and sealed by top and bottomannular disks 26 and 28. The nitrogen shield is supported by -a thermalgrounding flange 30 and removably attached thereto by bolts (notshown)which secure the disk 26 to the flange. The flange 30 is attached to thethin-walled tube '16 by means of a fused metal joint, e.g., bysoldering, brazing or welding It performs a dual function of mechanicalsupport and of cooling the inner tube 16 to a temperature approachingthat of the liquid refrigerant in the annular chamber 20. The chamber 2%communicates with the exterior of the vessel through one or more tubes.32, used for filling and venting purposes. The tubes 32 are surroundedby outer tubes 36, and the tubes 36 in turn are surrounded by packingwhere they penetrate the top plate 14, to provide avacuum-tight joint.For this purpose, I prefer to use elastomer O ring gaskets 34 in slidingjoints, which provide also for motion to accommodate diiferentialcontraction resulting from temperature changes in As best seen in FIG.2, this arrangement also facilitatesrernoval of the annular chamber 20by unbolting the thermal grounding flange .36 and withdrawing thechamber downward with respect to the top plate 14.

With further reference to FIG. 1, theouter tubes 35 are disposed about,and slightly spaced from, the tubes 32. They are welded only tattheirtop ends, above theplate 14, to the tubes 32. As noted below, there is avacuum in the space below the tubes 36 and thus, also in the spacesbetween the tubes 32 and 3 6. This .vacuurrnconrbined with therelatively high thermal impedances of the tubes 32 and 36, servestothermally isolate the tubes 32 from the O ring gaskets34, which are intightcontact with the tubes 36. Thus, the gaskets 34 are essentially atroom temperature, even when liquid nitrogen is poured into the chamber20 through one of the tubes 32.

The sliding joint design shown is only an example of 'how to accomplishdisassembly of the annular chamber 26 from the top plate 14.. Anotherapproach would be to V use bellows seals in the tubes 32, sleeves 36,tube 16, or grounding flange 30 to allow for differential contractionand disassembly.

Surrounding the housing 24 of the annular chamber as and separated fromit by a second vacuum insulation space 38 is anouter shell 40, whichserves to support the entire structure and to maintain a vacuum tightenvelope around the insulation space 38.

The outer shell 40 is attached to the top plate 14 by means of a boltedflanged joint 42.and is closed at the bottom by a similar bolted flangedjoint generally indicated at 44. More specifically, a flange plate 46 isbolted to an interior flange 48 aflixed to the shell 40. V

A flange plate 50 is bolted to the annular disk 28 at i the bottom ofthe chamber 20 to complete the intermediate sertion into confiningauxiliary apparatus such. as, an electromagnet gap.

Since the tail section 61,1comprising plates 46, 59 and 52 and theirextensions, may be readily removed from the Dewar body, generallyindicated at 62, a wide variety of extensions or appendages may beinterchangeably employed to accommodate varying experimentalrequirements with the same Dewar body.

The bolted flanged joint 42 between the outer shell 48 and the top plate14 facilitates the removal of the inner chamber (housing 12) and theannular chamber 2% (casings 22 and 24) as a unit, thereby exposing thechamber structure for repair or modification. The bolted joint betweenthe thermal grounding flange and the "chamber 20 structure, togetherwiththe sliding feature of the joints between the tubes 32 and 36 andthe top plate 14 permits disassembly of the housing 12 from the annularchamber20. FIG. 2 is'an exploded view showing the mannerin whichdisassembly is accomplished. Disassembly in this manner provides readyaccess to all joints in the entire structure for repair or modification.

Preferably, the surfaces bounding the vacuum insulating 'spaces 18 and38 are specially treated to reduce their bolts connecting the plates 30and 50 to the disks 26 and 28 should not extend through the disks, inorder not to disturb the vacuum tight isolation between the chamber 20and the spaces 18 and 38.

It is well known to those schooled in the art thatthe vapor pressures ofthe commonly occurring vapors and gases at thetemperature of liquidhelium are extremely low. Only helium and hydrogen have vapor pressuresmeasurable by conventional vacuum gauges. Gasses and vapors with thenotable exception of helium, are rapidly condensed on a helium cooledsurface and are effectively liquid helium); The resulting extremely highvacuum in the spaces 18 and 38 eliminates thermal energy transport bythe mechanism of gaseous conduction, contributing substantially to highthermal efiiciency. On the other hand, in certain cases, it may bedesirable to isolate the vacuum spaces 18 and 38 from each other, inwhich case it is preferable to provide a valve between them which isopened when the Dewar vessel is under long-term operation.

The utilization of the vacuum pumping effect of a very cold surfacepermits the use of the elastomer gaskets 34 and also similar gasketsused to seal the flanged joints 42 and 44. Without this effect, thediffusion of gases through and the evolution of gases and vapors fromthe elastomer gaskets would result in an'increase in pressure in thevacuum insulation-spaces and thermal efliciency would be impaired. Byusing the pumping effect, the need for charcoal or other adsorbents inthe vacuum spaces is completely eliminated.

In this connection, it is noted that with the above construction, allthe elastomer gaskets, i.e., in the joints 42 and 44, as well as thegaskets 34, are essentially at room temperature, and therefore, theyoperate efficiently with their full resiliency.

The vacuum pumping effect of cold surfaces cooled by liquids other thanhelium is effective on many vapors, but cannot, of course, remove gaseshaving appreciable vapor pressure at the temperature of the liquidrefrigerant.

FIG. 3 shows a tail section 66 which may be substituted for the tailsection 61 of FIG. 1. The section 66 includes flanges 46a, 50a and. 52a,similar to their counterparts 46, 50 and 52. Also included are tubularextensions 56a, 58a and 60a, which are somewhat different from thecorresponding parts in FIG. 1.

More specifically, to provide visual or X-ray access to a sample 68 held,in a sample holder 70, a vacuum tight window 72 of quartz or the likeis provided in the section 56a. A corresponding aperture '74 extendsthrough the Wall of the extension 58a of the nitrogen shield. At thelower end of the extension 60a is a solid projection 76, to which thesample holder 70 is attached. Thus, the sample 63 is maintained at avery low temperature without being immersed in the helium.

It can thus be seen that I have provided a novel and improved device forutilization of the cooling effects of liquefied gases. A unique degreeof convenience and flexibility is provided, while maintaining a highorder of thermal efiiciency. The Dewar vessel can be readilydisassembled for repair ormodification, and the design permitssubstitution or. interchange of a wide variety of appendages or tailsections to facilitate the execution of many different experiments witha single Dewar body. The disassembly feature is enhanced by use ofintercommunicating vacuum insulating spaces to permit the vacuum pumpingeffect of a very cold surface to remove any gases or vapors evolved bydifiusion or effusion. from elastomer seals used in thedemountablejoints. A variety of constructional features have been provided forpurpose of increased convenience and efficiency.

It will be apparent to, those skilled in the art that many and .variedchanges and modifications could be made in may be made in the aboveconstructions without departing from the scope of the invention, it isintended that all matter contained in the above description or shown inthe accompanyingdrawings shall be interpreted as illustrative and not ina limiting sense. a

It is also to be understood that the following claim are intended tocover all of the generic and specific features of the invention which,as a matter of language, might be said to fall therebetween.

I claim:

1. A multi-walled vacuum insulated vessel comprising (a) an outer Vacuumshell, v

(b) an intermediate low temperature thermal'radiation shield havinginner and outer walls forming a chamber between them,

(c) an inner container, 7

(d) a first plate extending across and removably secured to a first endof said shell,

(e) a conduit extending from said inner container outwardly through saidfirst plate,

(7) first sealing means sealing the interior of said inner containerfrom the space around said inner container and within said outer shell,

(g) second sealing means sealing said chamber from said space, w

(h) a supporting structure for supporting said shield from said firstplate, and

(1') means removably securing said shield to said supporting structure.

2. The combination defined in claim 1 including (a) a tube extendingfrom the interior of said shield through said first plate, and

(b) means forming a hermetic seal between said tube and said first plateand permitting movement of said tube through said first plate.

3. The combination defined in claim 2 including means securing saidconduit to said first plate.

4. The combination defined in claim 2 including means forming apassageway between said hermetic seal and the exterior surface of saidinner container.

5. The combination defined in clairn 1 including a tail sectioncomprising a second plate extending across, removably secured to, andsealing a second end of said shell.

6. The combination defined in claim 5 (a) in which said inner and outerwalls are tubular,

and

(b) said chamber has a first end facing said first plate and a secondend facing said second plate, said first and second ends being definedby said second sealing means,

(0) said tail section including 1) a third plate extending across and inclose thermal contact with said second sealing means and spaced fromsaid second plate, and

(2) a fourth plate removably attached to said inner container andsealing an aperture therein opening toward said third plate.

7. A multi-walled vacuum vessel comprising (a) an inner container havinga first end and a second end,

(b) a thermal radiation shield (1) surrounding and spaced from saidinner container, and

(2) comprising first and second tubular walls, said second wallsurrounding and spaced from said first wall to form a chamber betweenthem,

(0) a tubular outer shell surrounding and spaced from said second wfll,

(d) a first plate extending across a first end of said shell andremovably secured thereto,

(e) a conduit 7 (1) communicating with the interior of said innercontainer and extending through said first plate from a first endthereof facing said first plate, and

(2) sealed to said first plate where it passes therethrough,

(f) first sealing means sealing said first end of said inner container,

(g) a second plate extending across the second end of said shell andremovably secured thereto,

e 6 (It) said first and second walls having (l) first ends defining afirst end of said chamber and facing said first plate, and -(2) secondends defining a second end of said chamber and facing said second plate,

(i) first and second sealing means sealing said first and second ends ofsaid chamber,

(j) a third plate extending across said second end of at least saidfirst tubular wall and removably secured thereto,

(k) a fourth plate extending across an aperture in said inner containeropening toward said third plate and removably secured to said innercontainer to seal said aperture,

(1) a fifth plate 7 (1) extending across said first end of said firsttubular Wall and removably secured thereto, (2) surrounding and aflixedto said conduit between said inner container and said first plate, (3)in close thermal contact with said chamber and said conduit.

8. The combination defined in claim 7 including (a) a tube communicatingwith the interior of said chamber and extending through said firstplate,

([2) means forming a seal between said tube and first plate permittingsaid tube to slide through said first plate.

9. The combination defined in claim 8 in which said sealing meansincludes (b) an elastomeric gasket between and contacting said secondtube and said first plate. 10. The combination defined in claim 9including means forming passageways between the outer surface of saidinner container, and e (a) the joints between said first and secondplates and said shell, and

(b) said gasket.

11. The combination defined in claim 7 including means formingpassageways between the outer surface of said inner container and thejoints between said first and second plates andshell.

12. The combination defined in claim 7 in which said second, third andfourth plates include first, second and third tubular extensions,respectively,

(a) said extensions being spaced apart from each other,

(b) said extensions extending away from said first plate,

(a) said first extension surrounding said second extension, and

(d) said second extension surrounding said third extension.

13. The combination defined in claim 12 including (a) means for securingan object within said second extension and in close thermal contact withsaid third extension,

(b); means forming an aperture in said second extension,

(0) a window in said first extension,

(d) said window and said aperture being disposed in a line'extendingthrough said object.

14. The combination defined in claim 2 including means communicatingbetween (a) the space between said outer shell and said radiation shieldand (b) the space between said shield and said inner container.

(Ref erenees on following page) 7. V References Cited by the ExaminerUNITED STATES PATENTS V 9/60 Fong .1 62--514 3,066,222 11/62 Poorman eta1. 62-414 OTHER REFERENCES Cryogenics, March 1962. Article by Chopra onpp.

8 6 (Copy in Scientific Library and in 167-169 relied on.

Group 380, 62-45.)

Instruments and Experimental Techniques, July- August 1960 (U.S.S.R.),No. 4. Article by Fradkov on pp. 126-130 relied on. (Translated copy inGroup 380,

ROBERT A. OLEARY, Primary Examiner.

1. A MULTI-WALLED VACUUM INSULATED VESSEL COMPRISING (A) AN OUTER VACUUMSHELL, (B) AN INTERMEDIATE LOW TEMPERATURE THERMAL RADIATION SHIELDHAVING INNER AND OUTER WALLS FORMING A CHAMBER BETWEEN THEM, (C) ANINNER CONTAINER, (D) A FIRST PLATE EXTENDING ACROSS AND REMOVABLYSECURED TO A FIRST END OF SAID SHELL, (E) A CONDUIT EXTENDING FROM SAIDINNER CONTAINER OUTWARDLY THROUGH SAID FIRST PLATE, (F) FIRST SEALINGMEANS SEALING THE INTERIOR OF SAID INNER CONTAINER FROM THE SPACE AROUNDSAID INNER CONTAINER AND WITHIN SAID OUTER SHELL, (G) SECOND SEALINGMEANS SAEALING SAID CHAMBER FROM SAID SPACE, (H) A SUPPORTING STRUCTUREFOR SUPPORTING SAID SHIELD FROM SAID FIRST PLATE, AND (I) MEANSREMOVABLY SECURING SAID SHIELD TO SAID SUPPORTING STRUCTURE.